US4273900A - Diaphragm for acoustic equipment - Google Patents

Diaphragm for acoustic equipment Download PDF

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Publication number
US4273900A
US4273900A US06/055,780 US5578079A US4273900A US 4273900 A US4273900 A US 4273900A US 5578079 A US5578079 A US 5578079A US 4273900 A US4273900 A US 4273900A
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United States
Prior art keywords
diaphragm
block copolymer
film
acoustic
diaphragms
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Expired - Lifetime
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US06/055,780
Inventor
Kosaku Murata
Satoshi Takayama
Mitsuru Ieki
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K13/00—Cones, diaphragms, or the like, for emitting or receiving sound in general
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
    • C08G63/66—Polyesters containing oxygen in the form of ether groups
    • C08G63/668—Polyesters containing oxygen in the form of ether groups derived from polycarboxylic acids and polyhydroxy compounds
    • C08G63/672—Dicarboxylic acids and dihydroxy compounds
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R7/00—Diaphragms for electromechanical transducers; Cones
    • H04R7/02—Diaphragms for electromechanical transducers; Cones characterised by the construction
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/31504—Composite [nonstructural laminate]
    • Y10T428/31786—Of polyester [e.g., alkyd, etc.]

Definitions

  • the present invention relates to a diaphragm for acoustic equipment having excellent low-pitched sound reproducing performance and flat acoustic pressure-frequency characteristics.
  • polyethyleneterephthalate, Mylar (tradename) and Lumilar are mainly used in small diameter speakers, for example, in tweeters, in speakers for a small-sized radio receivers, and in speakers for headphones.
  • plastic film diaphragms have a higher elasticity and a small inner loss, strain might develop during sound reproduction.
  • the lowest resonant frequency f o of speaker is given by the following equation: ##EQU1## (wherein S o is the stiffness in the diaphragm supporting portion, and m o is the effective mass of the vibration system).
  • diaphragms made of such film have a high S o and hence, as apparent from the above equation, also a high f o , usually about 600 Hz, making it difficult for them to reproduce low-pitched sounds. If S o is lessened by reducing the film thickness to improve the low-pitched sound reproducing characteristics of the polyethyleneterephthalate film diaphragm, divisional resonance is produced in the diaphragm causing strains to develop during reproduction. It was thus difficult to improve the acoustic characteristics of plastic film diaphragms.
  • the present inventors have conducted further studies to improve the properties, particularly acoustic characteristics, of the conventional types of speaker diaphragms, particularly those made of plastic film, and have succeeded in developing a diaphragm prepared from a polyester-polyether block copolymer for acoustic equipment having quite satisfactory properties.
  • An object of the present invention is to provide a diaphragm for acoustic equipment having an excellent low-pitched sound reproducing performance and flat acoustic pressure-frequency characteristics.
  • the sole FIGURE illustrates pressure-frequency characteristics of diaphragms of the prior art and those of the present invention.
  • a diaphragm for acoustic equipment that is prepared from polyester-polyether block copolymer mainly consisting of polytetramethyleneterephthalate having a rigidity as the hard segment of the diaphragm and poly(tetramethyleneoxide)glycol having rubber-like elasticity as the soft segment of the diaphragm.
  • the feature of said block copolymer is that the elasticity of the copolymer can easily be controlled by adjusting the amount of poly(tetramethyleneoxide)glycol as the soft segment in the block copolymer.
  • the present diaphragm Since the inner loss of the present diaphragm is within the range of 0.04 to 0.20, which is large as compared with that 0.007 of conventional polyethyleneterephthalate film (for example, Mylar film), the present diaphragm provides a better acoustic reproducing performance.
  • FIGURE is the acoustic pressure-frequency characteristic of speaker diaphragms.
  • Curves (a) and (b) indicate the characteristics of the diaphragms according to the present invention and curve (c) indicates the characteristic of a conventional speaker diaphragm.
  • the polyethyleneterephthalate film is pressed under heating in a die to form the predetermined shape, and the molded product is removed from the die which is at once cooled to facilitate the removal of the product. If the molded product is removed from the die without cooling the die, then the molded product would be deformed resulting in an undesirable shape, so that it is difficult to obtain a product having predetermined shape. Moreover, it requires a much longer period of time to run the molding operation.
  • the diaphragm of block copolymer of the present invention can be molded under vacuum in a pressurized condition, so that the productivity of manufacturing the diaphragm is greatly increased.
  • the present block copolymer film is subjected to a corona-discharge treatment and just after the treatment, a synthetic rubber type adhesive material, such as chloroprene or neoprene, is coated on the surface of the film treated by corona discharge, and then the block copolymer film coated with the adhesive is effectively subjected to a molding operation for making a diaphragm of predetermined shape for a desired acoustic equipment such as a speaker.
  • a synthetic rubber type adhesive material such as chloroprene or neoprene
  • the block copolymer film thus made was subjected to a corona-discharge at 110 KHz and at 4 K volts. Then the corona-discharged surface of the film was coated with an adhesive mainly consisting of chloroprene to form an adhesive layer having a thickness of 1 to 1.4 ⁇ m.
  • the treated copolymer film has a size of 100 mm in width and 70 ⁇ in thickness. Elasticity modulus of this film was 1700 kg/cm 2 and inner loss was 0.15.
  • a predetermined shaped diaphragm was made by using a vacuum press die. Small-sized speakers for headphones were made from this diaphragm having a 40 mm diameter with a 125 ⁇ impedance.
  • Elasticity modulus of this block copolymer film was 1200 kg/cm 2 and inner loss was 0.17.
  • the adhesion strengths between diaphragm and voice coil and between diaphragm and frame of the diaphragms obtained in Examples 1 and 2 were excellent and no troubles were observed in actual use. Additionally, according to weathering evaluation test conducted by using a weatherometer, if an ultraviolet absorber is added to the present diaphragm a durability 1.5 times longer than that of a diaphragm without the untraviolet absorber is attained. Furthermore no changes in the acoustic characteristics were observed in the diaphragm containing the ultraviolet absorber after the weathering evaluation test.
  • curves (a) and (b) indicate the acoustic pressure-frequency characteristics of the speakers respectively made of the diaphragms prepared and shaped from the block copolymer film obtained in Examples 1 and 2.
  • Curve (c) indicates the acoustic pressure-frequency characteristics of the speaker made of a diaphragm of conventional polyethyleneterephthalate film molded in the same shape having 70 ⁇ in thickness.
  • the speakers using the diaphragms of the present invention show excellent low-pitched sound reproducing performance.
  • the lowest resonant frequency f o of the speaker made of diaphragm of conventional polyethyleneterephthalate film is 780 Hz
  • the lowest resonant frequency f o of the speakers made of diaphragms obtained in Examples 1 and 2 of the present invention are respectively 480 Hz and 350 Hz, which show flat acoustic pressure-frequency characteristics, particularly, at the middle region of the frequency scale.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Physics & Mathematics (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Signal Processing (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)

Abstract

A diaphragm for acoustic equipment molded from a composition mainly consisting of a polyester-polyether block copolymer prepared by condensing a polytetramethylene-terephthalate with a poly(tetramethyleneoxide)glycol or any other polyester-polyether block copolymer. This diaphragm for acoustic equipment has an excellent low-pitched sound reproducing performance and flat acoustic pressure-frequency characteristics.

Description

This is a continuation of U.S. Pat. application Ser. No. 903,798 filed May 8, 1978, now abandoned.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to a diaphragm for acoustic equipment having excellent low-pitched sound reproducing performance and flat acoustic pressure-frequency characteristics.
Conventional speaker-diaphragms are usually made from a cone shaped paper. Organic plastic film diaphragms such as polyethyleneterephthalate films have also been used for the same purpose.
Among these prior art diaphragm materials, polyethyleneterephthalate, Mylar (tradename) and Lumilar are mainly used in small diameter speakers, for example, in tweeters, in speakers for a small-sized radio receivers, and in speakers for headphones. However, since plastic film diaphragms have a higher elasticity and a small inner loss, strain might develop during sound reproduction.
Thus, in general, the lowest resonant frequency fo of speaker is given by the following equation: ##EQU1## (wherein So is the stiffness in the diaphragm supporting portion, and mo is the effective mass of the vibration system).
Since the conventional polyethyleneterephthalate film has a large elastic modulus, diaphragms made of such film have a high So and hence, as apparent from the above equation, also a high fo, usually about 600 Hz, making it difficult for them to reproduce low-pitched sounds. If So is lessened by reducing the film thickness to improve the low-pitched sound reproducing characteristics of the polyethyleneterephthalate film diaphragm, divisional resonance is produced in the diaphragm causing strains to develop during reproduction. It was thus difficult to improve the acoustic characteristics of plastic film diaphragms.
The present inventors have conducted further studies to improve the properties, particularly acoustic characteristics, of the conventional types of speaker diaphragms, particularly those made of plastic film, and have succeeded in developing a diaphragm prepared from a polyester-polyether block copolymer for acoustic equipment having quite satisfactory properties.
An object of the present invention is to provide a diaphragm for acoustic equipment having an excellent low-pitched sound reproducing performance and flat acoustic pressure-frequency characteristics.
BRIEF DESCRIPTION OF THE DRAWING
The sole FIGURE illustrates pressure-frequency characteristics of diaphragms of the prior art and those of the present invention.
DETAILED DESCRIPTION
According to the present invention, there is provided a diaphragm for acoustic equipment that is prepared from polyester-polyether block copolymer mainly consisting of polytetramethyleneterephthalate having a rigidity as the hard segment of the diaphragm and poly(tetramethyleneoxide)glycol having rubber-like elasticity as the soft segment of the diaphragm. The feature of said block copolymer is that the elasticity of the copolymer can easily be controlled by adjusting the amount of poly(tetramethyleneoxide)glycol as the soft segment in the block copolymer.
As the result, according to the present invention, various types of acoustic equipment, such as speakers, can be freely designed and thus various types of requirements in designing the acoustic equipment can be successfully fulfilled.
Since the inner loss of the present diaphragm is within the range of 0.04 to 0.20, which is large as compared with that 0.007 of conventional polyethyleneterephthalate film (for example, Mylar film), the present diaphragm provides a better acoustic reproducing performance.
The accompanying FIGURE is the acoustic pressure-frequency characteristic of speaker diaphragms. Curves (a) and (b) indicate the characteristics of the diaphragms according to the present invention and curve (c) indicates the characteristic of a conventional speaker diaphragm.
Furthermore, drawbacks encountered in the prior art in manufacturing acoustic diaphragms prepared from polyethyleneterephthalate can not be seen in case of manufacturing diaphragms using the block copolymer of the present invention.
Thus, in molding to make a polyethyleneterephthalate diaphragm, the polyethyleneterephthalate film is pressed under heating in a die to form the predetermined shape, and the molded product is removed from the die which is at once cooled to facilitate the removal of the product. If the molded product is removed from the die without cooling the die, then the molded product would be deformed resulting in an undesirable shape, so that it is difficult to obtain a product having predetermined shape. Moreover, it requires a much longer period of time to run the molding operation.
On the contrary, the diaphragm of block copolymer of the present invention can be molded under vacuum in a pressurized condition, so that the productivity of manufacturing the diaphragm is greatly increased.
Generally, there are some problems such as poor adhesiveness between the diaphragm and a voice coil or between the diaphragm and a frame rises which are troublesome when the diaphragm is made of a conventional polymer material. In the present invention, however, such problems can be solved by surface-treating the block copolymer film. Various types of techniques for treating the surface of plastic film are known in the art. In one method of surface-treating the plastic film, the present block copolymer film is subjected to a corona-discharge treatment and just after the treatment, a synthetic rubber type adhesive material, such as chloroprene or neoprene, is coated on the surface of the film treated by corona discharge, and then the block copolymer film coated with the adhesive is effectively subjected to a molding operation for making a diaphragm of predetermined shape for a desired acoustic equipment such as a speaker. According to a peel test of the diaphragm (for example, aluminium to chloroprene peel test at 180° peeling), a sufficient adhesion strength between the copolymer film and aluminium was obtained due to a plastic deformation occurring in the block copolymer.
The present invention will be illustrated in further detail by way of the following examples.
EXAMPLE 1
Block copolymer pellets consisting of poly(tetramethyleneoxide)glycol having molecular weight of 1000 as the soft segment and polytetramethyleneterephthalate as the hard segment, said copolymer having the mole ratio of [terephthalic acid part]:[poly(tetramethyleneoxide)glycol]=7:1 and also containing 0.3 part of 2-hydroxy-4-n-octoxy benzophenone as a ultraviolet absorber per 100 parts of the copolymer, were dried at 110° C. for 24 hours and then extruded by using a screw extruder having a diameter of 25 mm at 240° C. with T-die of 300 mm×0.6 mm, and cooled on chill roll at 50° C. The block copolymer film thus made was subjected to a corona-discharge at 110 KHz and at 4 K volts. Then the corona-discharged surface of the film was coated with an adhesive mainly consisting of chloroprene to form an adhesive layer having a thickness of 1 to 1.4 μm. The treated copolymer film has a size of 100 mm in width and 70μ in thickness. Elasticity modulus of this film was 1700 kg/cm2 and inner loss was 0.15. A predetermined shaped diaphragm was made by using a vacuum press die. Small-sized speakers for headphones were made from this diaphragm having a 40 mm diameter with a 125 Ω impedance.
EXAMPLE 2
A block copolymer film was prepared by the method similar to that described in Example 1, but instead a block copolymer was used consisting of poly(tetramethyleneoxide)glycol having a molecular weight of 1000 as the soft segment and polytetramethyleneterephthalate as the hard segment, said copolymer having the mole ratio of [terephthalic acid part]:[poly(tetramethyleneoxide)glycol]=10:1.
Elasticity modulus of this block copolymer film was 1200 kg/cm2 and inner loss was 0.17.
The adhesion strengths between diaphragm and voice coil and between diaphragm and frame of the diaphragms obtained in Examples 1 and 2 were excellent and no troubles were observed in actual use. Additionally, according to weathering evaluation test conducted by using a weatherometer, if an ultraviolet absorber is added to the present diaphragm a durability 1.5 times longer than that of a diaphragm without the untraviolet absorber is attained. Furthermore no changes in the acoustic characteristics were observed in the diaphragm containing the ultraviolet absorber after the weathering evaluation test.
In the accompanying FIGURE, curves (a) and (b) indicate the acoustic pressure-frequency characteristics of the speakers respectively made of the diaphragms prepared and shaped from the block copolymer film obtained in Examples 1 and 2. Curve (c) indicates the acoustic pressure-frequency characteristics of the speaker made of a diaphragm of conventional polyethyleneterephthalate film molded in the same shape having 70μ in thickness. As apparent from the FIGURE, the speakers using the diaphragms of the present invention show excellent low-pitched sound reproducing performance.
The lowest resonant frequency fo of the speaker made of diaphragm of conventional polyethyleneterephthalate film is 780 Hz, while the lowest resonant frequency fo of the speakers made of diaphragms obtained in Examples 1 and 2 of the present invention are respectively 480 Hz and 350 Hz, which show flat acoustic pressure-frequency characteristics, particularly, at the middle region of the frequency scale.

Claims (4)

What is claimed is:
1. A diaphragm for a sound transducing device having a lowest resonant frequency lower than or equal to 480 Hz and an inner loss between 0.04 and 0.20 which is prepared by molding a composition mainly consisting of a copolymer of poly (tetramethyleneoxide) glycol with polytetramethyleneterephthalate.
2. A diaphragm as in claim 1, wherein the molar ratio of terephthalic acid moiety to poly (tetramethylene-oxide) glycol is in the range of about 10:1 to about 7:1.
3. A diaphragm as in claim 2, wherein said ratio is 10:1.
4. A diaphragm as in claim 2, wherein said ratio is 7:1.
US06/055,780 1977-05-07 1979-07-09 Diaphragm for acoustic equipment Expired - Lifetime US4273900A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP52/262 1977-05-07
JP5226277A JPS53137129A (en) 1977-05-07 1977-05-07 Vibratory diaphragm for acousitic device

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US05903798 Continuation 1978-05-08

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US4273900A true US4273900A (en) 1981-06-16

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US06/055,780 Expired - Lifetime US4273900A (en) 1977-05-07 1979-07-09 Diaphragm for acoustic equipment

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JP (1) JPS53137129A (en)
CA (1) CA1100665A (en)
DE (1) DE2819786C3 (en)
GB (1) GB1587047A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019237604A1 (en) * 2018-06-15 2019-12-19 歌尔股份有限公司 Speaker diaphragm and speaker
WO2019237609A1 (en) * 2018-06-15 2019-12-19 歌尔股份有限公司 Loudspeaker diaphragm and loudspeaker
WO2019237602A1 (en) * 2018-06-15 2019-12-19 歌尔股份有限公司 Loudspeaker diaphragm and loudspeaker
EP3809718A1 (en) * 2018-06-15 2021-04-21 Goertek Inc. Loudspeaker

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5871798A (en) * 1981-10-26 1983-04-28 Sony Corp Dynamic headphone
JPS61292499A (en) * 1985-06-20 1986-12-23 Matsushita Electric Ind Co Ltd Diaphragm for speaker
CA1298058C (en) * 1987-04-15 1992-03-31 Peter Shewchuk Threaded mounting for extruded pole
DE3831706A1 (en) * 1988-09-17 1990-03-22 Bayer Ag MEMBRANE FOR SPEAKERS

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3674109A (en) * 1969-08-26 1972-07-04 Nippon Musical Instruments Mfg Thermo-plastic laminated structure
US3963800A (en) * 1973-12-04 1976-06-15 Bayer Aktiengesellschaft Thermoplastically processable elastomeric copolyester
US4004960A (en) * 1975-04-07 1977-01-25 Usm Corporation Copolyester-amide resin and adhesive processes
US4059715A (en) * 1975-06-30 1977-11-22 Minnesota Mining And Manufacturing Company Adhesive composition and sheet-like product formed therewith
US4064098A (en) * 1975-10-27 1977-12-20 Mitsui Petrochemical Industries Ltd. Glass fiber-reinforced poly(tetramethylene terephthalate) resin composition

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3674109A (en) * 1969-08-26 1972-07-04 Nippon Musical Instruments Mfg Thermo-plastic laminated structure
US3963800A (en) * 1973-12-04 1976-06-15 Bayer Aktiengesellschaft Thermoplastically processable elastomeric copolyester
US4004960A (en) * 1975-04-07 1977-01-25 Usm Corporation Copolyester-amide resin and adhesive processes
US4059715A (en) * 1975-06-30 1977-11-22 Minnesota Mining And Manufacturing Company Adhesive composition and sheet-like product formed therewith
US4064098A (en) * 1975-10-27 1977-12-20 Mitsui Petrochemical Industries Ltd. Glass fiber-reinforced poly(tetramethylene terephthalate) resin composition

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2019237604A1 (en) * 2018-06-15 2019-12-19 歌尔股份有限公司 Speaker diaphragm and speaker
WO2019237609A1 (en) * 2018-06-15 2019-12-19 歌尔股份有限公司 Loudspeaker diaphragm and loudspeaker
WO2019237602A1 (en) * 2018-06-15 2019-12-19 歌尔股份有限公司 Loudspeaker diaphragm and loudspeaker
EP3809718A1 (en) * 2018-06-15 2021-04-21 Goertek Inc. Loudspeaker
US11317211B2 (en) 2018-06-15 2022-04-26 Goertek Inc. Speaker diaphragm and speaker
EP3809719A4 (en) * 2018-06-15 2022-05-25 Goertek Inc. Speaker diaphragm and speaker
EP3809718A4 (en) * 2018-06-15 2022-05-25 Goertek Inc. Loudspeaker
EP3809722A4 (en) * 2018-06-15 2022-06-15 Goertek Inc. Loudspeaker diaphragm and loudspeaker
US11818559B2 (en) 2018-06-15 2023-11-14 Goertek Inc. Speaker diaphragm and speaker

Also Published As

Publication number Publication date
DE2819786B2 (en) 1979-08-02
JPS53137129A (en) 1978-11-30
DE2819786C3 (en) 1980-04-10
DE2819786A1 (en) 1978-11-23
CA1100665A (en) 1981-05-05
GB1587047A (en) 1981-03-25
JPS5641040B2 (en) 1981-09-25

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